Manufacture of lead pigments.



, assassin snares PATENT curios.-

SLEL FGEJJ 33. HULLEY, 075 DETROIT, MICHIGAN, ASSIGNOR' TO ACME WHITE LEAD tfiim 130L919; WORKS, (3F DETROIT, MICHIGAN, A CORPORATIQN OF MICHIGAN.

EMNUEACTUBE F LEAD PIGMENTS.

Specification of Letters Patent.

PatentcdDec.30,1913.

. Filo Drawing. Application filed finish 3, 1911, Eerialito. 512,029. Renewed April 4, 1915;. Serial No. 758,956.

To, all whom "it may concern I Be it brown that l, Gourono' D. Homer, :1 citizen-of the United-S ates, residln at Detroihlin the county of "aync and tate 0 Michigan, have invented certain new and useful Improvements in the Manufacture of Lead Pigments, of which the following is a specification. This invention relates to the manufacture of lead pigments; and it comprises a rocass of producing lead oxid pi cents w erelid in basic lead oxide are heats with a solution of a nitinte for the purpose of modifying the character of such oxids, the resulting mixture being then further treated, as by evaporation and furnacing, to obtain valuable pi eats; all as more fully hereinafter est birth and as claimed.

in the manufacture of red lead and similar lead onid pigments, it s the common practice first to produce a massicot which my be described as a relatively unstable and potentially reactive monoxid of lead, and

then to treat the massicot under suitable conditions to in the desired pigment. A good red lea? should be amorphous, of rather low specific gravity, and should consistvery largely of ibt), with only a small percentage of unconverted monoxid (PbO).

A crystalline, dense red lead containing much unconverted PbO is practically worthless for pigmentary purposes. The physical and chemical characteristics of red lead depend almost entirely upon those of the particular massicot from which it was made. Massicot' may be made by dressing metallic lead under carefully'controlled furnace conditions, as regards temperaturc,-etc.,; but

a better method is to make it by furnacing certain kinds of basic oxids of lead, the temperature and other conditions being narrowly regulated as in the-dressing method. The great diificulty heretofore in attempting to produce massicot from basic oxids has been that on account of the extremely variable character of such oxide, it was impossible by the methods proposed to obtain mussicots of uniform quality and possessing all, the physical and chemical characteristics requisite for the production of a high grade lead therefrom. Massicot slinurily produced from basic oxids of lead ishighlv unsatisfactory, being often relatively inert and slow to take up oxygen; so that when such massicot 1s Iurnaced to obtain red lead,

'fercnces in the the percentage of conversion is far below I produced from basic oxids 0 lead is probably due almost entirely in the first instance to the widely varying characteristics of the basic oxids themselves.

Basic lead oxids may be obtained by, a variety of processes, as for example, by at-' trition processes, which depend in'gencral upon agitating and aerating masses of finely divided lead in water, The basic oxids obtained in these processes vary widcl in physical and chemical properties accord ing to the particular process employed, slight variations in procedure causing unexpectedly Wide variation in the characteristics of the basic oxids produced. More: over the quality of basic oxids produced in any one of these attrition processes is liable to considerable variation, in spite of the greatest care to standardize the process in all details. Slight differences in the size of charge treated, the size of the lead particles'forming the charge, the amount and, quality of the water employed, the extent of aeration, the temperature of operation, etc, all cause disproportionately great di'fsulting basic oxids as re-' gards their physical and chemical properties. Basic oxids thus produced range in i0.

color from greenish yellow, through yellow and orange, to brownish red; and their phys ical and chemical properties vary as widely as do their colors. crystalline in structure, relatively stable and inactive in character, and of alow degree 95 of basicit-y. Such oxids do not take up Y oxygen readily to form red lead; in fact their conduct in this respect is similar to that of litharge which maybe termed a fixed or stable monoxid and which, as is well 100 known, is not suitable for the manufacture of red lead owing to its nonreactive-character. Other basic oxids of lead may be amorphous or even gelatinous in form, and

chcmically are unstable, extremely reactive, 105

and highly basic in character. These highly basic oxids culd be Well suited to red lead making, but linfortunstcly it has not been possible commercially to produce themconsistcntly and'uniformly by any of the proc- 12'} Some are coarsely r esses hitherto known. Between the two ex.- l

treme types of basic oxids described above, vizrthei stable inert oxid, and the unstable, highly basic reactive oxid, are'many inter mediate types partaking more or less of the characteristics of both extremes. At best,

the product obtained from any of the pro-- posed processes of making basic lead oxidsis always a mixture of many of the various basic oxide abcve referred to. A part of the oxids n the mixture may chance to be fairly reactive and can be converted rather readily into red lead; but large proportions of the mixed oxids are relatively inert and in the furnacingoperation fail altogether to take up oxygen to form red lead or do so only with the greatest difliculty. Red lead produced from mixtures such as these is almost invariably. of inferior quality, and often is he mass even. when .stirred.

practically Worthless as pigment.

Another objection to basic oxids of lead as heret ')fore producedis'th at they are prone to assume an undesirable hysical condition when furnacedu When t e mass of mixed basic oxid's is subjected to furnace treatment in order to secure dehydration of the oxids and a more complete conversion of the;

temperature must be regulated within very lem becomes a diificult one tov solve.

narrow limits. At too low temperatures the desired reactions'occur not at all .or only inefficiently,f while if thegtemperature is slightly too high, dissociation of the product occurs and the-reaction proceeds backward. If the temperature is allowed to become high enough to produce-fusion, litharge andsimilar oxids result, and in making massicbt and red lead, litharge is of course a highly un desirable product; The p1'0-blem of properlydistributing the furnace heatthrough the mass of basic oxids undergoing treatment is one of the greatest'importance, and on account of the tendency of such oxids when furnaced to form a dense powder,'the prob-- Fun thermore the .massicot obtained from such powdered oxidsis of such a soft adhesive, clinging] nature, that when subsequently milled and separated for the purpose of re ducing whatever coarse particles maybe present and removing all unconverted lead particles, the rinding operation is rendered extremely dil cult. Such niassicot cl ngs to the sides of the grinding mill and builds up into-soft masses which frequently dislodge themselves and choke the mill, putting it temporarily out of service. a

l have discovered that by suitably treatosaess ing the basic oxids as they are ordinarily obtained, it is possible to modify. their chemical and physical properties in such a manner that. they are rendered entirelv suitable for producing massicot,'red lead, and other forms of lead oxids without encountering the difiicnlties usually met. .For ex-. ample, I may mix the. basic oxide produced by any of the various attrition processes and which may contain varying percentages of residual metallics or unconverted particles of metallic lead, with a solution of a nitrate, as an alkali nitrate, and then heat the mixture. 0r the nitrate solution'may-be first heated and then mixed with the oxids. It is best in any case finally to bring the mix ture to a boil and to keep at or near the boiling temperature for some time." It is also advantageous as a rule to add, asmall percentage ofnitric acid, where the Basic oxids contain as they ordinarily lip, Tennsiderable amountsof admixed uncoiivert-eiil metallic lead particles. Inproducing basic 'oxids of lead by attritionprocesses, theoxids may form at first on the surfaces of the lead particles with comparative ease. But after these first formed oxide are rubbed, off and new lead surfaces of lead are exposed, thc oxidizing reaction for some reason does not proceed so actively, and finally it stops while 1 there is still, a considerable part ofthe lead particle left unconverted. If these so-called residual metallics are separated from the basic oxids and an attempt is made to con vert them further by attrition, it is found that for some reason practically no conversion to basic oxid occurs. The nucleus of the original lead particle seems to have been altered in some way during the early stages of the attrition process in such a manconditions of that process. For the purpresence of such residual metallics ofiers no diliicultics. The nitric acid attacks and oxidizes these metallicparticles renderingthe action of the nitrate solution -more .ef-X

'105 ner'that 1t,1s no longer reactive under the any residual metallics are prescnt, a small amount of nitric acid is advantageous. -Afte'r the boiling operation, the liquid is evaporated from the mixture without any pre-.-' vious separation, and this evaporation should occur at relatively low temperatures,

say at about the boilin point of water, andmay be carried on an er reduced ressure, though this isnot essential. The evaporation is continued until the mass is substantially dry. The resultingfroduct isa mass" of hydrated oxids of lea and reactive character, with which is mixed a small amountof-nitrites resulting from reduction of the nitrate employed in the of highly basic 1 process. Moreover th 5 ,chemical alterability, when the oxids are sizes instead of falling penetration of .heat to I ing soft, clin 2 quent conversion i geneity and high 95 per cent.

0 may be carbonated the carbon 40 fact the chemist 5 ple from the unconverted particl ev process has changed of the oxids, impartcr'ispness andcohertim'e enhancing their the physical charactering to them a peculiar. once while at the same furnacedthey react readily and yet remain in lumps of various into a dense poiiider oxids. F

all parts of the mass res uniformity in the as do the untreated easyto obtain and'insu product. i Massicot p roduced from basic oxids' treated according to my new process, instead of be} ging, and adherent, is crisp, and is very easily separated from es of metallic lead. This condition of the massicot arly applicable to subsemills freely,

desirable physical makes it particul degree of reactivity enable be accomplished with great this descripad analyzing in character the conversion to.

tion it is'easy to obtain 'ared le Pb' O voluminous" and of excellent tint.

Instead of being evaporated downimmediately after boiling with the nitrate solution, the Wet mass of hydrated basicoxid by treating with carbon dioxid in the usual Way and then dried to yield a good quality ofWh-ite lead, which may be used as such or furnacedto produce oxid pigments such as orange mineral. Or

ating may follow a partial evaporation; but 111 any. case the carbonating should pr cede the furnacing.

The exact chemical-reactions involved inmy new process are more or less obscure; in ry of the hydrated basic lead oxids in general is quite complex and not fully understood. What appears to occur is a kind of homogenizing action whereby the heterogeneous hasic oxids obtained for examso-called attrition processes, are rendered comparatively uniform in composition and of approximately the same degree of hydration and basicity. This homogenizing act-ion is accompanied by a marked alteration in physical structure as above nitrate at by this'process, the re or less non-reactive it has hitherto aking massicot noted. The result is th 'imsatisfa tory, and mo variable asic oxide, which been attempted to use for m and red lead, are so modified as to give basic oxids of uniform composition, of highbasicity and; reactivity, and of particularly advantageous physical structure.

In carryingout my invention find it best to employ alkali nitrates, sodium nitrate being particularly suitable. Other nitrates such as those of the alkaline earths,- lead nitrate, etc., can be used but they offer no special advantages. The proportion of employed may vary widely. The

practically I with the result. that -.This renders ntored lead, and its homopresence of a small amount of nitric acid is also usually advisable for the reason that basic qxids as produced commercially generally contain varying percentages of residual metallics orpartic which are attacked and oxidized by the acid, the acid itself. being reduced largely to am moniain the react-ion. .The Waste liquors from chrome yellow or lead chromate, which contain sodium or potassium nitrate and some nitric'acid,s.are well suited for use in the present PI'OCGSS. The sodium or potassium nitrate is reduc nitrite during the: boiling process and remains in the-evaporated mass, its presence being or advantage ing to produ'ce'red lead, Where it acts as an oxygen carrier. "The nitrite appears as such in the finished red lead and it maybe leached therefrom if desired and recovered, being a valuable material used inythe azo dye and color industries. Where the percentage of nitrite in the finished red lead does not exceed one-fourth of'one per cent. it may erally. but not necessarily, be allowed to remain in'the product, since in that quantity its presence does no harm.

In a specific embodiment'of my I'may miX'QOO gallons of Water in which are dissolved 10 pounds of sodium nitrate and 20 pounds of nitric acid, with 5,000 pounds of the ordinary mixed basic lead oxids produced by any of the ordinary attrition processcs, and after thorough mixing, heat the mixture to boiling. The boiling is continued for about 30 minutes and the mixture is then evaporated to approximate dryness at or near the temperature of boiling. The resulting mass of modified basic oxids is then dchydrated and converted into massicot by a furnacing process, and from the massicot thus produced red lead may be made byan appropriate oxidation.

What I claim isz- 1. The process of ments which comprises oxids to-thc action of once ofa relatively large amount of water, removing the excess of Water, and treating the resulting mass to obtain lead pigments.

2. The process of producing lead pigments which comprises adding Water and an alkali nitrate to a basic lead oxid, heating the mixture, or dryness, and furnacing the residue to produce massicot.

l 3. The process of ises adding Water and c lead oxid, heating" to proximate invention,

producing load piga nitrate in the presments which compr sodium nitrate to a basi the mixture, cvaporatin dryness, and furnacing duce massicot. v

4., The process of producing ments which comprises subjecting lead oxid containing les of unconverted lead.

subjecting basiclcad' aporating to approximate producing lead p glead pig ed to a corresponding 1n a subsequent fur'nacgen- I v .125 t e resi ue'to proresidual: metallics the action of a nitrate and a minimal amount, of. nitric acid inthe'presence of'a relatively treating the residue to obtain lead pigments.

7. The process of producing lead pigments which comprises boiling a basic lead oxid with a water solution of sodium nitrate, removing the major portion of the water from the mixture, and treating the residue to obtain lead pigments.

8. The process of producing lead ,pigments which'compr-isesboiling a basic lead oxidwith a Water solution of sodiuni nitrate and nitric acid, removing the'major portion .of the water from the mixture, and treating the residue to obtain lead pigments.

9. The process of producing lead pigments which comprises heating a mixture of a basic oxid of lead with Water containa ing sodium nitrate and nitric acid, evaporating off most of the water, and treating the residue to obtain massicotand red lead. 10. The process of producing lead oxids which comprises heating a mixture of commercial basic oXids of lead with a water so lutlon ofa nitrate. I

. 11. The process of producing lead oxide which comprises heating a mixture of lead oxid with a water solution of a nitrate and nitric acid.

' 12. The process of producing lead o-xids which comprises mixing a basic lead oxid with an excess of a water solution of an alkali nitrate, and boiling the mixture. r

13. The process of producing lead oxids which comprises'mixing a basic lead oxid with an excess of a water solution of analkali nitrate and nitric acid, and boiling the mixture.

14. The process of producing lead oxids which comprises mixing a basic lead oxid with an excess of a water solution of sodium nitrate and nitric acid and boiling the mixture.

15. The process of producing lead'oxidswhich comprises mixing a basic lead oxid.

with an excess of a water solution of sodium ture and evaporating to approximate dryness.

ments which comprises adding to a mess of basic lead oxids containing admixed particles of metallic lead a relatlvely large quantity of water containing sodium nitrate and nitric acid, heating the mixture to boiling,

evaporating off substantially all of the wa tar, and furnacing the residue to produce niassicot and red lead.

In testimony whereof I affix my signature iii the presence of witnesses.

, CLIFFORD D. HOLLEY.

N. J. PErIM, H. WATKINS.

a basic 16. The process of producing lead pig- 6O nitrate and nitric acid, boiling the inix- 

